1. Field of the Invention
The present invention relates to semiconductor devices.
2. Description of the Related Art
In recent years, identification technology in which an ID (identification number) is assigned to an individual object to clarify the history of information thereof, which is utilized for production, management, or the like has attracted attention. In particular, an RFID (radio frequency identification) such as an RF tag (also referred to as an ID tag, an IC tag, an IC chip, a wireless tag, or an electronic tag) which is a semiconductor device capable of communicating data wirelessly with a wireless communication device (which can transmit and receive a signal wirelessly, such as a reader/writer, a mobile phone, or a personal computer) (hereinafter referred to as a semiconductor device) has been introduced on a trial basis to markets, and the like and anticipated to be applied to various fields. Semiconductor devices include a passive semiconductor device which does not have a power source and receives power externally and an active semiconductor device which incorporates a power source.
Being capable of communicating data wirelessly with a wireless communication device, a semiconductor device can communicate even in a case where the distance from the wireless communication device is long. The distance over which communication is possible is referred to as communication distance. Communication distance of a passive semiconductor device which does not have a power source is greatly affected by performance of a rectification function of a transmitting and receiving circuit and varies in accordance with conversion efficiency at the time of generation of a DC voltage from received power. Communication distance of an active semiconductor device which incorporates a power source affects efficiency (time) in charging the power source. Therefore, research and development for improving supply efficiency of power from a wireless communication device to a semiconductor device have been actively carried out in order to extend communication distance between the wireless communication device and the semiconductor device (for example, Patent Document 1: Japanese Published Patent Application No. 2006-5651).